Laforin, the most common protein mutated in Lafora disease, regulates autophagy

Lafora disease (LD) is an autosomal recessive, progressive myoclonus epilepsy, which is characterized by the accumulation of polyglucosan inclusion bodies, called Lafora bodies, in the cytoplasm of cells in the central nervous system and in many other organs. However, it is unclear at the moment whether Lafora bodies are the cause of the disease, or whether they are secondary consequences of a primary metabolic alteration. Here we describe that the major genetic lesion that causes LD, loss-of-function of the protein laforin, impairs autophagy. This phenomenon is confirmed in cell lines from human patients, mouse embryonic fibroblasts from laforin knockout mice and in tissues from such mice. Conversely, laforin expression stimulates autophagy. Laforin regulates autophagy via the mammalian target of rapamycin kinase-dependent pathway. The changes in autophagy mediated by laforin regulate the accumulation of diverse autophagy substrates and would be predicted to impact on the Lafora body accumulation and the cell stress seen in this disease that may eventually contribute to cell death

Fiber Type Conversion by PGC-1α Activates Lysosomal and Autophagosomal Biogenesis in Both Unaffected and Pompe Skeletal Muscle

PGC-1α is a transcriptional co-activator that plays a central role in the regulation of energy metabolism. Our interest in this protein was driven by its ability to promote muscle remodeling. Conversion from fast glycolytic to slow oxidative fibers seemed a promising therapeutic approach in Pompe disease, a severe myopathy caused by deficiency of the lysosomal enzyme acid alpha-glucosidase (GAA) which is responsible for the degradation of glycogen. The recently approved enzyme replacement therapy (ERT) has only a partial effect in skeletal muscle. In our Pompe mouse model (KO), the poor muscle response is seen in fast but not in slow muscle and is associated with massive accumulation of autophagic debris and ineffective autophagy. In an attempt to turn the therapy-resistant fibers into fibers amenable to therapy, we made transgenic KO mice expressing PGC-1α in muscle (tgKO). The successful switch from fast to slow fibers prevented the formation of autophagic buildup in the converted fibers, but PGC-1α failed to improve the clearance of glycogen by ERT. This outcome is likely explained by an unexpected dramatic increase in muscle glycogen load to levels much closer to those observed in patients, in particular infants, with the disease. We have also found a remarkable rise in the number of lysosomes and autophagosomes in the tgKO compared to the KO. These data point to the role of PGC-1α in muscle glucose metabolism and its possible role as a master regulator for organelle biogenesis - not only for mitochondria but also for lysosomes and autophagosomes. These findings may have implications for therapy of lysosomal diseases and other disorders with altered autophagy

In vitro effects of hormones and autacoids on the activity of acid phosphatase in the lysates of endotoxin-activated rat peritoneal and bronchoalveolar macrophages

Peritoneal and bronchoalveolar macrophages activated in vitro by endotoxin, exhibit alterations in the acid phosphatase activity of cell lysates when certain hormones or autacoids are present in the culture medium. They also show morphological changes concerning general appearance and acid phosphatase cytochemistry. Certain agents known to increase the intracellular levels of cyclic AMP, such as dopamine and prostaglandin E2, decreased this enzyme activity in the lysates of peritoneal macrophages. Adrenalin had no effect on this activity at 14 hours, but was found to increase the activity in the culture medium at the initial hours of incubation. Glucagon decreased whereas insulin increased acid phosphatase activity in bronchoalveolar macrophages. Serotonin or histamine, known to activate phospholipase C, increased this activity in peritoneal or bronchoalveolar macrophages. The results of this study, taken together with previously published data (Kondomerkos et al., 2003), suggest that hormones and autacoids may control certain parameters of macrophage activation including acid phosphatase activity

In vitro effects of hormones and autacoids on the hydrogen peroxide production and the morphology of endotoxin-activated rat peritoneal macrophages

Peritoneal macrophages activated in vitro by endotoxin exhibit alterations of their capability to produce hydrogen peroxide after phorbol ester stimulation when certain hormones or autacoids are present in the culture medium. They also show morphological changes, mainly concerning cell size and nuclear appearance. Agents known to increase the intracellular levels of cyclic AMP, e.g. adrenalin and PGE2 reduce the hydrogen peroxide production. Insulin, which is known to decrease cyclic AMP levels, produces opposite results. Agents postulated to act via phospholipase C, e.g. serotonin, augment the production of hydrogen peroxide. We assume that this form of modulation may represent a regulatory mechanism of macrophage activation

Glycogen autophagy in the liver and heart of newborn rats. The effects of glucagon, adrenalin or rapamycin

The effects of glucagon, adrenalin or rapamycin on glycogen autophagy in the liver and heart of newborn rats were studied using biochemical determinations and electron microscopy. Glucagon or adrenalin increased autophagic activity in the hepatocytes and myocardiocytes, glycogen-hydrolyzing acid glucosidase activity in the liver and heart and degradation of glycogen inside the autophagic vacuoles. Glucagon or adrenalin also increased the maltosehydrolyzing acid glucosidase activity in the liver, but not in the heart. Similar effects were produced in the newborn heart by rapamycin. These observations support previous studies suggesting that the cellular machinery which controls glycogen autophagy in the liver and heart of newborn animals, is regulated by the cyclic AMP and the mTOR pathways